Potassium is a chemical found throughout the body. It helps our cells, tissues and organs function properly.

98% of the body’s potassium lives inside our cells. Only 2% is found in the water (serum) in our blood stream. Still, the only practical way to measure whether we have the right amount of potassium is with a blood test.

The normal serum potassium level is 3.5 to 5.0 milliequivalents per liter. But most healthy people have potassium levels of 3.8 or higher.

Doctors refer to a low serum potassium level as hypokalemia.

• 3.0 to 3.4 is mild hypokalemia
• 2.5 to 2.9 is moderate hypokalemia
• Less than 2.5 is severe hypokalemia

Most people with mild hypokalemia will have minimal or no symptoms. The symptoms that they can have are fatigue, weakness and muscle cramps. Moderate and severe hypokalemia can cause marked fatigue and muscle weakness.

Hypokalemia is most worrisome in people who have heart disease. A low potassium level increases the chance of a heart rhythm problem. This is sometimes a dangerous situation.

The most common cause of hypokalemia is diuretic use. Other causes include:

• Using laxatives
• Overusing short-acting asthma inhalers
• Vomiting
• Eating disorders
• Diarrhea>

There are several other rarer causes, too.